Circuit arrangement for power windows

Claim 1

A safety control circuit for the electric motor of a power window for automotive vehicles which senses the motor current and differentiates between a tight fitting of the window pane and an obstacle blockage, said control circuit comprising, in combination: first means for selectively applying and reversing operating current to said motor wherein said first means applies said operating current to said motor in a selected one of two current directions to reverse the output motion direction of said motor and removes said operating current to stop said motor; second means for detecting the operating current of said motor for providing a first output signal indicative thereof; third means having an input coupled to said second means and being responsive to said first output signal for providing a second output signal indicative of the instantaneous value of said first output signal; fourth means for providing a reference signal indicative of a predetermined instantaneous operating current level; fifth means having a pair of inputs respectively coupled to said third and fourth means for comparing said reference signal to said second output signal and for providing a third output signal when the level of said second signal exceeds the level of said reference signal during a predetermined time period; and, a switching element coupled between said first means and said fifth means and being responsive to said third output signal to remove or reverse said operating current from said motor when the level of said second signal exceeds the level of said reference signal during said predetermined time period.